Homeomorphy in Lunostoma, a new Middle Devonian cryptostome bryozoan

A new genus and species of rhabdomesine cryptostome bryozoan, Lunostoma pulchra n. gen. n. sp., is described from the Lower Givetian (Middle Devonian) of the Eifel, Germany. It differs from all previously known rhabdomesines in having crescent-shaped structures (??scuta??) on the proximal sides of the apertures. These scuta resemble the lunaria that characterise cystoporate bryozoans, providing yet another example of homeomorphy in the Bryozoa. The function of scuta is unclear as, in contrast to lunaria, they do not project sufficiently from the apertures to constrain the everting lophophores.     

Autecology of Labrocuspis, a Middle Devonian omphalotrochid gastropod

Labrocuspis kobayashii , a Middle Devonian euomphalacean omphalotrochid gastropod from Japan has a wide callus pad on its base similar to that seen in the living trochid Umbonium. L. kobayashii could support the shell over the cephalopedal mass in a similar fashion to that seen in the Umbonium species. This reconstruction indicates that the labral projection in the outer lip was above the head, and the opisthocyrt basal lip and the sinus in the outer lip were loci of inhalant and exhalant currents, respectively. Therefore, the animal is assumed to have had only one ctenidium (the left). The presence of a wide callus pad is indicative of an infaunal life habit for the Umbonium species, Labrocuspis and some Paleozoic gastropods; clamping of the shell against the foot is also suggested for some omphalotrochid gastropods. These features indicate an additional adaptive strategy employed by euomphalaceans.     

Cyrtinoides Yudina and Rzhonsnitskaya, 1985, an aberrant Middle Devonian ambocoeliid brachiopod genus from China

Here we redescribe and reillustrate specimens of an ambocoeliid brachiopod previously described as Echinocoelia guangsiensis Sun, 1992 from the late Eifelian–earliest Givetian Mingtang Formation of the Liujing section in Guangxi Autonomous Region. The internal structure of the species, and especially the presence of a spondylium with tichorhinum in the ventral valve indicates that the species represents the aberrant genus Cyrtinoides Yudina and Rzhonsnitskaya, 1985. It seems probable that the anterior part of the tichorhinum in Cyrtinoides accommodated the diductor attachments. Geographic distribution of Cyrtinoides is restricted to the Northern Hemisphere and shows a disjunct pattern. This genus has not hitherto been identified from China.     

Unusual skeletal morphology and systematic description of a new Devonian cryptostome bryozoan from the Western Sahara

Palaeozoic bryozoan colonies display a large variety of skeletal elements. Various types of rod-like styles are mainly built by laminated and non-laminated (hyaline) skeleton. Typical styles consist of hyaline cores and surrounding laminated sheaths. They usually protrude on the colony surface as spines. In a new bryozoan genus from the Middle Devonian of the Western Sahara described here, styles do not protrude on the colony surface and are embedded within the laminated skeleton. They consist of fibrous material. This new type of styles, unknown from other bryozoans, is here called a “cryptostyle”. A special characteristic of these structures is their intensive reddish-brown colouration. This colouration is apparently caused by the presence of ferric iron between the individual fibres. The function of cryptostyles was apparently weight reduction and stabilising the skeleton. The general morphology of the new bryozoan, Cryptostyloecia hexapuncta gen. et n. sp., implies its systematic position within ptilodictyine cryptostomes, specifically the Family Ptilodictyidae Zittel, 1880.     

Biochemistry and structural DNA nanotechnology: an evolving symbiotic relationship

Structural DNA nanotechnology is derived from naturally occurring structures and phenomena in cellular biochemistry. Motifs based on branched DNA molecules are linked together by sticky ends to produce objects, periodic arrays, and nanomechanical devices. The motifs include Holliday junction analogues, double and triple crossover molecules, knots, and parallelograms. Polyhedral catenanes, such as a cube or a truncated octahedron, have been assembled from branched junctions. Stiff motifs have been used to produce periodic arrays, containing topographic features visible in atomic force microscopy; these include deliberately striped patterns and cavities whose sizes can be tuned by design. Deliberately knotted molecules have been assembled. Aperiodic arrangements of DNA tiles can be used to produce assemblies corresponding to logical computation. Both DNA structural transitions and branch migration have been used as the basis for the operation of DNA nanomechanical devices. Structural DNA nanotechnology has been used in a number of applications in biochemistry. An RNA knot has been used to establish the existence of RNA topoisomerase activity. The sequence dependence of crossover isomerization and branch migration at symmetric sites has been established through the use of symmetric immobile junctions. DNA parallelogram arrays have been used to determine the interhelical angles for a variety of DNA branched junctions. The relationship between biochemistry and structural DNA nanotechnology continues to grow.     

Larval apical sensory organ in a neritimorph gastropod,an ancient gastropod lineage with feeding larvae

The Neritimorpha is an ancient clade of gastropods that may have acquired larval planktotrophy independently of the evolution of this developmental mode in other gastropods (caenogastropods and heterobranchs). Neritimorphs are therefore centrally important to questions about larval evolution within the Gastropoda, but there is very little information about developmental morphology through metamorphosis for this group. We used immunolabeling (antibodies binding to acetylated α-tubulin and serotonin) and serial ultrathin sections for transmission electron microscopy to characterize the apical sensory organ in planktotrophic larvae of a marine neritimorph. The apical sensory organ of gastropod larvae is a highly conserved multicellular sensory structure that includes an apical ganglion and often an associated ciliary structure. Surprisingly, the apical ganglion of Nerita melanotragus (Smith, 1884) does not have typical ampullary neurons, a type of sensory neuron consisting of a cilia filled inpocketing that has been described in all other major gastropod groups. N. melanotragus has cilia-filled pockets embedded within the apical ganglion, but these so-called “sensory cups” are cassettes of multiple cells: one supporting cell and up to three multiciliated sensory cells. We suggest that an internalized pocket that is filled with cilia and open to the exterior via a narrow pore may be essential architectural features for whatever sensory cues are detected by ampullary neurons and sensory cups; however, morphogenesis of these features at the cellular level has undergone evolutionary change. We also note a correlation between the number of sensory elements consisting of cilia-filled pockets within the larval apical sensory organ of gastropods and morphological complexity of the velum or length of the trochal ciliary bands.     

Restudy and reassignment ofDentalium antiquum Goldfuss, 1841 (Middle Devonian)

Dentalium antiquum is one of two moderately well-known Devonian “scaphopods” in the German literature. Examination of the type material and a few specimens in other institutions indicates more individual variability than is to be expected in species of the molluscan class Scaphopoda. The species is transferred with question toColeolus Hall, a fossil presumed to be a calcareous “worm” tube.      

Stratigraphy, geometry, and facies of a Middle Devonian ramp-to-basin transect (Eastern Anti-Atlas, SE Morocco)

Summary In the castern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Basin) evolved during the late Palacozoic. The Middle Devonian deposits consist of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures and sole marks of Middle Devonian limestones indicate transport from the northwest and the south towards the basin centre, located in the central Mader area. Lithostratigraphic, biostratigraphic, and dynamic stratigraphic approaches were applied to correlate stratigraphic sections. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian succession. Thickness trends of Middle Devonian deposits, regional correlations, and facies-trends reveal the geometry of a carbonate ramp. The carbonate ramp was slightly inclined (<1°) to the NE. A sedimentary wedge, consisting of limestones and limestone/marl alternations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp and far below storm wave-base in the northeastern part of the ramp. Shallowest conditions (inner-ramp environment), close or within the fairweather wave-base, existed during the early Givetian as documented by the abundance of recfal fauna (stromatoporoids, corals) and calcimicrobes (lumps, micritic envelopes) in the eastern and southeastern area of the ramp.     

A new boring bryozoan from the Middle Jurassic of the Moscow Region and its micro-CT research

A new boring ctenostome bryozoan without calcareous skeleton, Orbignyopora opulenta sp. nov. (Vesiculariida, Eurystomata), is described from deposits of the Middle Callovian of the Moscow Region. A pioneering micro-ct examination of a colony of this species reveals its diagnostic features hidden in the shell substratum: shape, size, and distinctive features in the budding of zooids and stolons, and also tubular processes (tubulets) developed on the frontal surface of autozooids. The diagnosis of the genus Orbignyopora is added by dimorphism of autozooids (A-zooids and B-zooids) and spindly kenozooids.     

A new Middle Devonian gasterocomid crinoid from central Turkey and revision of the Gasterocomidae

A juvenile cup, disarticulated arm plates, and columnals of the crinoid Arachnocrinus sarizensis n. sp. are described from the Eastern Taurus Mountains of central Turkey. This is the first Paleozoic crinoid based on a cup and arm plates reported from Turkey. Suggested revision of the Gasterocomidae includes transfer of Arachnocrinus and Ancyrocrinus to the family and rejection of Kopficrinus from the family. The stratigraphic range of Arachnocrinus is extended upward into the Middle Devonian from the Early Devonian. The Devonian of Turkey is of special interest because it includes Laurasian and Gondwanan components on different tectonic blocks. The paleogeographic range of Arachnocrinus is extended from the North American plate onto the Anatolian block, which would have been located on the southern edge of the Paleotethys Sea in the Middle Devonian in a shelf basin off the northern coast of Gondwana at approximately 42° south latitude.     

Integrated Middle Devonian chitinozoan and miospore zonation of the Amazonas Basin, northern Brazil

Middle Devonian chitinozoans were studied from 13 deep wells in the central part of the Amazonas Basin, northern Brazil, and compared with a newly established regional miospore zonation. Of the 23 chitinozoan species encountered, four are newly described: Ancyrochitina multibrachiata, Lagenochitina praeavelinoi, Ramochitina autasmirimense, and Ramochitina herculesi and seven species are retained in open nomenclature because of an insufficient number of well-preserved specimens. The stratigraphic intervals investigated herein correspond to three miospore interval range zones previously defined for the Amazonas Basin, namely, the Grandispora/Samarisporites spp. (GS); late Emsian-early Eifelian, Grandispora permulta (Per); late early Eifelian through the Eifelian-Givetian transition, and Geminospora lemurata-Chelinospora ex. gr. ligurata (LLi); early Givetian. A regional Middle Devonian chitinozoan biozonation, also consisting of three zones, is proposed for the investigated interval. These zones are the interval zone of Angochitina n. sp. A (early Eifelian), the interval zone of Alpenachitina eisenacki (late early to late Eifelian), and the total range zone of Ramochitina stiphrospinata (early Givetian).     

Miospore stratigraphy of Lower and early Middle Devonian deposits from Tidikelt, Central Sahara, Algeria

The Tidikelt region forms an outstanding area for subsurface Lower Devonian stratigraphy in the central Algerian Sahara. Sediments from five boreholes have revealed abundant and diverse assemblages of miospores, acritarchs, chitinozoa, scolecodont and microplant remains. The miospores are moderately well preserved. Three new miospore species (Dibolisporites saharansis nov. sp. Hassan Kermandji, Acinosporites conatus nov. sp. Hassan Kermandji and Scylaspora tidikeltense nov. sp. Hassan Kermandji) are described. Miospore assemblages vary through the regressive and transgressive sequences. Seven miospore assemblage biozones, including six new miospore assemblage biozones (Scylaspora tidikeltense-Perotrilites microbaculatus, Dictyotriletes emsiensis-Emphanisporites spinaeformis, Apiculiretusispora arenorugosa-Camptozonotriletes caperatus, Verrucosisporites polygonalis-Dictyotriletes subgranifer, Emphanisporites annulatus-Geminospora svalbardiae, Hystricosporites microancyreus-Grandispora protea, Calyptosporites velatus-Rhabdosporites langii) are proposed for the Lower and early Middle Devonian rocks of Tidikelt Plateau. The combined use of distinctive, wide distribution cosmopolitan and Gondwanan forms as biozonal and species characteristics permits accurate subdivision, dating and correlation of Tidikelt successions with other similar miospore zones of the Lower Devonian of Europe, Canada and other parts of Gondwana plate. The miospore data provide new explanations to stratigraphic relationships of regional rock units, sedimentary cycles and stratigraphic hiatus. The miospore biozones are proposed as a provincial biozonation, which may also be applied to other Palaeozoic rocks of similar miospore content.     

Growth forms and palaeoenvironmental interpretation of stromatoporoids in a Middle Devonian reef, southern Morocco (west Sahara)

Growth forms of well-preserved stromatoporoids, including genera Actinostroma, Stachyodes, and Stromatopora, are described for the first time from the Devonian Sabkhat Lafayrina reef complex of southern Morocco (west Sahara), one of the best exposed Middle-Devonian stromatoporoid-dominated fossil reefs. Three facies types representing the well illuminated fore-reef, reef-core and transition to back-reef facies display the distribution and growth of stromatoporoids in a high latitude setting at 40–50° south of the palaeoequator. Stromatoporoids are largely in growth position and reflect the well-preserved reef architecture. Although outcrops are low topography, the reef's prominent profile is indicated by presence of spur and groove form and a clearly defined reef margin. Stromatoporoids are mostly laminar and domical forms, with little evidence of ragged margins, and indicate normal turbulence shallow waters, with low sediment deposition.     

A neotype for Coipodexylon gracilentum Dou (Lycopsida) from the Middle Devonian of North Xinjiang, China

According to newly collected and well preserved specimens,herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang,NW China are reduced to C.gracilentum,for which a neotype is designated and emended diagnosis is given.Colpodexylon gracilentum has leaves with three nearly equal segmems,an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.     

A neotype for Colpodexylon gracilentum Dou (Lycopsida) from the Middle Devonian of North Xinjiang,China

According to newly collected and well preserved specimens,herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang,NW China are reduced to C.gracilentum,for which a neotype is designated and emended diagnosis is given.Colpodexylon gracilentum has leaves with three nearly equal segments,an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.     

Bryozoans, corals, and microfacies of Lower Eifelian (Middle Devonian) limestones at Kierspe, Germany

The Lower Eifelian Meinerzhagener Korallenkalk (= upper Cultrijugatus Beds) at Kierspe, Sauerland, contains a rich reefal fauna. Eight bryozoan species are described, two of them are new: the cystoporate Fistuliporella kierspensis n. sp. and the trepostome Leptotrypella sophiae n. sp. The bryozoans from the Meinerzhagener Korallenkalk shows distinct similarities to the Lower–Middle Devonian of Spain (Santa Lucía Formation, Emsian–Eifelian), and to the Middle Devonian (Eifelian) of Transcaucasia. The coral fauna comprises five tabulate corals and one rugose coral that document a paleobiogeographic relationship between Central and Eastern Europe and Central Asia. The associated fauna is represented by brachiopods, ostracods, and echinoderms. The studied limestones also commonly contain calcimicrobes represented by three species. The faunal and microfacial characteristics indicate a shallow marine depositional environment just above the storm wave base, with a supposed depth of 20 m, within the photic zone. The nutrient regime was at least a mesotrophic. The upper boundary of the Cultrijugatus Beds coincides with the Chote?-Event that strongly affected brachiopods, whereas corals and bryozoans were insensitive to this event.     

Plumatella mukaii,a new phylactolaemate bryozoan from Asia and South America

A new freshwater bryozoan species, Plumatella mukaii, is recognized from eastern Asia and western South America. Colonies and statoblasts both bear a resemblance to P. emarginata, and have often been confused with that species, especially in Japanese studies. Floatoblasts and sessoblasts are enclosed within a tough, wrinkled, membrane which resists removal by mechanical means. Floatoblasts are generally smaller than those of P. emarginata, but display unusually high variability in their overall dimensions. The species has been reported from both lentic and lotic habitats. In Asia, the range includes Japan, Korea, China, India and Indonesia. It has most recently also been found at several sites in Chile. The recognition of P. mukaii narrows the previously reported range of P. emarginata and invites a re-inspection of that species worldwide.     

Phylogenetic relationship within the Erythrobasidium clade: molecular phylogenies, secondary structure, and intron positions inferred from partial sequences of ribosomal RNA and elongation factor-1alpha genes

Phylogenetic relationships within the Erythrobasidium clade as a lineage of the urediniomycetous yeasts were examined using partial regions of 18S rDNA, 5.8S rDNA, 26S rDNA, internal transcribed spacers (ITSs), and elongation factor (EF)-1alpha. Combined data analysis of all segments successfully yielded a reliable phylogeny and confirmed the cohesion of species characterized by Q-10(H2) as a major ubiquinone. Differences in secondary structure predicted for a variable region in 26S rDNA corresponded to major divergences in the phylogenetic tree based on the primary sequence. The common presence of a shortened helix in this region was considered to be evidence of monophyly for species with Q-10(H2), Sakaguchia dacryoides, Rhodotorula lactosa, and Rhodotorula lamellibrachiae, although it was not as strongly supported by the combined data tree. The information on intron positions in the EF-1alpha gene had potential usefulness in the phylogenetic inference between closely related species.     

A circa-decadal change in the gastropod fauna on a tidal flat in an island mangrove estuary

An investigation on gastropod fauna was carried out on a tidal flat in the Nagura Estuary on Ishigaki Island, the Ryukyu Islands in 1989 and 1998 using similar methods. 470-480 quadrats covering ca. 1900 m2 were surveyed during low tides from February to April in each year. Of the total 19 species recorded, the ranges of eight species had varied significantly between the two surveys, with six species expanding their range and two species contracting their range. Percentage in abundance of muddy-bottom species and tropical (<29 degrees N) species increased significantly between the two years. Topography of the flat also changed: the mouth of the river was narrowed and the elevated sections of the tidal flat expanded. During the period from 1984 to 1998, the farmland development around the study site caused influxes of soil into the estuary and the sea-water temperature was rising. These results suggest that the topographical changes due to soil influx and the rising temperature affected the gastropod assemblage at the study site, by increasing the abundance of muddy-bottom species and tropical species. The methodology used in this study, i.e. surface observation at low tides, includes more than 95% of the gastropod fauna, demonstrating the usefulness of surface counts for the study of soft-bottom fauna.     

Impact of plant nutrients on the relationship between a herbivorous insect and its symbiotic bacteria

The interactions between herbivorous insects and their symbiotic micro-organisms can be influenced by the plant species on which the insects are reared, but the underlying mechanisms are not understood. Here, we identify plant nutrients, specifically amino acids, as a candidate factor affecting the impact of symbiotic bacteria on the performance of the phloem-feeding aphid Aphis fabae. Aphis fabae grew more slowly on the labiate plant Lamium purpureum than on an alternative host plant Vicia faba, and the negative effect of L. purpureum on aphid growth was consistently exacerbated by the bacterial secondary symbionts Regiella insecticola and Hamiltonella defensa, which attained high densities in L. purpureum-reared aphids. The amino acid content of the phloem sap of L. purpureum was very low; and A. fabae on chemically defined diets of low amino acid content also grew slowly and had elevated secondary symbiont densities. It is suggested that the phloem nutrient profile of L. purpureum promotes deleterious traits in the secondary symbionts and disturbs insect controls over bacterial abundance.